Organosilicon lubricants



United States Patent ORGANOSILICON LUBRICANTS 5 John J. May, Midland,Mich., asslgnor to Dow Corning iCorporation, Midland, Mich., acorporation of Michgan No Drawing. Application September 8, 1952 SerialNo. 308,531

8 Claims. (Cl. 252-496) Y This invention relates to organosiliconlubricants. The lubricants of this invention comprise mixtures of fluidorganosiloxanes having the'general formula R;.si0, T

where n has an average value of from 2.0 to 2.9 and R may be methyl,monocyclic aryl, halogenated aryl hydrocarbon, or mixtures thereof andfrom 0.25 percent by weight to 5 percent by weight, based on thesiloxane, of a halogenated fatty acid having one to 12 carbon atoms.

Siloxane lubricants are well known for their ability to withstandextreme temperature conditions, e. g. temperatures at which petroleumoil lubricants can not be 9 used. However, at ordinary temperatures,these known siloxane lubricants compare very unfavorably to thepetroleum lubricants in general lubrication properties.

At the present time no known siloxane lubricant can be satisfactorilysubstituted for petroleum lubricants for use at ordinary temperatures,"particularly where high pressure conditions exist and when bearingsurfaces are both steel.

Although siloxane lubricants have been much improved for high pressureuse (e. g. boundary lubrication) such as those described and claimed inthe copending application of Chester C. Currie, Serial No. 270,771, nowU. S. Patent No. 2,642,395, assigned to the same assignee as thisinvention, they still leave much to be desired when compared withorganic lubricants at ordinary temperatures. It is the object of thisinvention to prepare siloxane lubricants which not only have theheretofore known utility at high and low temperatures, but which alsocompare favorably with petroleum oil at ordinary temperatures.

The objects of this invention are obtained merely by admixinghalogenated fatty acids having 1 to 12 carbon atoms with the siloxanefluid. The halogenated fatty acids may be employed in amounts rangingfrom 0.25 to 5 percent by weight based on the siloxane. No advantage isgained in employing amounts larger than 5 percent. 5 The advantages ofthis invention are only partially obtained by employing amounts smallerthan 0.25 percent. Any halogenated fatty acid having from 1 to 12 carbonatoms is operative in this invention. The preferred acids are the alphaand/or beta halogenated fatty acids having 1 to 6 carbons in which thehalogen is bromine or chlorine. No advantage is ordinarily gained byemploying acids halogenated beyond the tri-, or tetra-halo stage.Specific examples of operative acids are dichloroacetic acid,alphabromocaproic acid, trichloroacetic acid, alpha-chloropropionicacid, alpha-bromopropionic acid, alpha-bromobutyric acid,beta-chloropropionic acid, alpha, beta-dichlorobutyric acid,alpha-chlorovaleric acid, gammabromovaleric acid, bromoor chloro-capricacids, the chloroand bromo-lauric acids and iodo-acetic acid.

The above acid additives may be simply admixed with the siloxane fluid,employing ordinary mixing equipment.

Mixing may occasionally be facilitated by moderate warmmg. p

The siloxane fluids which are employed in this invention are thosehaving the general formula I where n has an average value of from 2.0 to2.9 and where R is methyl, aryl hydrocarbon, or halogenated arylhydrocarbon radicals, or any mixture of such radicals. It is preferred,however, that at least 37 percent of the total number of R radicals inthe siloxane fluid be methyl. In this invention R may be, for example,methyl, phenyl, tolyl, iodotolyl, dichlorophenyl, heptachloroxenyl,dichloroxenyl, bromophenyl and dibromoxenyl. 1

Preferred are theftriorganosilyl endblocked dimethylsiloxane fluids andmethylphenylsiloxane fluids. These fluids are well known in the art andcommercially available. Al'so' preferred are'the halogenated aryl'siloxane fluid copolymers described and claimedfin' U; S. Patent No.2,599,984. Methods of preparing the s'iloxane fluids employed in thisinvention are well known in the art.

The siloxa'ne lubricants of this invention may be readily compoundedinto greases by admixing with various known thickening agents, as forexample, metallic salts of higher fatty acids such as lithium stearate,graphite, clay, carbon black, silica gels, fumed silica, etc. Methods ofpreparing siloxane greases are well known in the art. Preferably theacids of this invention are milled into the grease.

Other additives well known in the lubrication field such asanti-oxidizing agents may be added to the mixtures. of this invention.

The mixtures of compositions of this invention were tested on a Falexlubricant testing machine. This machine is commercially used in thelubrication" industry and from it may be obtained measurements whichaccurately indicate the ability of the lubricant to prevent wear betweenmoving metal parts under pressure; The operation and nature of the Falexmachine is described'by Victor A. Ryan in Lubrication Engineering,September 1946, pp. 102-104. f

'The *test substantially involves rotating a shaft between two'V-blocksas pressure is applied to the bearing surface. The resulting wear ofshaft'and the V-block when operated under agiven load for a given periodof time is measured by means of a ratchet wheel. The wear is expressedin teeth wear, one tooth wear being equal to .0000556 inch of wear'indepth. a

The lubricants of this invention were tested at room temperature in thefollowing manner. I i r The Falex machine employing steel'V-blocks andsteel shafts was started and a load of 50 pounds gauge was applied in amachine run offive minutes. At the end of this period load loss wasnoted and tooth wear ismeasured. The load was readjusted to 50 lbs.(to-compensate for load loss, if any) and a machine run for a secondfive minutes is made after which the above observations were againnoted. Next a pound load was applied over two five minute intervals inthe samemanner observing load loss and tooth wear in each interval asbefore, and finally a 200 pound load is applied over two five minuteintervals in identical manner. I

In Table 1 of Example 1 the total load loss (L) and total tooth wear (T)of the six successive intervals mentioned in the preceding paragraph aretotaled. Since both load loss and tooth wear are essential for properevalua'tion of a lubricant, a factor consisting of their product dividedby 100 has been included in the .table to-make comparison more clear. Inthe examples all mixtures weretested 'over the sixintervals mentionedabove unless otherwise indicated.

The followingexar'nple's illtis ever, the scope of this invention islimited only as set forth in the claims.

EXAMPLE 1 mixtures, of Table. 1 were prepared employing a commercialtriinethylsiloxy end-blocked dimethylsiloxane polymer having a viscosityof 350 Cs. at 25 C. The additives as listed in column 1, of the tablewere directly mixed into the siloxane by means of laboratory stirrers.The amount of additive added is tabulated as per cent by weight based onthe siloxane.

. intuit, V Additive 2% Dichloroacetic acid. I

2% alpha-Bromocaproic acid. 6% Trichloroacetic acid.

. 5% Dlchloroacet ic acid.

2% alpha-Chloropropionic acid. 2% alpha-Bromopropionlcacid. 2%alpha-Bromobutyric acid. 1% beta-Chloropropionic acid.

l-8, inclusive, were tested on the Falex machine in accordance with thetest above described with the results as shown in Table 1.

EXAMPLE 2 The efiect of the additives of this invention upon a fluidsiloxane composed of mol percent C H CH SiO units, 75 mol percent .(CHSiO, units and percent (CH SiO units is shown in Table 2 below. MixtureA consists of the siloxane without additive, andmixture B consists ofthetsiloxane to which has been added 2 percent by weight (based on thesiloxane) of alphabromobutyric acid. Themixtures A and B were tested inthe manner of Example 1.

Table 2 Mixture 1'. T E

a 100 314 2,198 B V 47 45 21 Table3 shows the. effect of the addition ofalphahromobutyric acid to a siloxane fluid composed of .45 mol percentphenylmethylsiloxane units, 45 mol percent dijm'ethylsiloxane units. (CHSiO, and 10 mol percent trimethylsiloxane units (CH5) SiO g,.whentestedin accordance with Example 1. Mixture A is without additive;

trate this invention. How- 7 mixture B has 2% by weight (based on thesiloxane) alpha-bromobutyric acid.

Table 3 Mixture L '1 100 A 700 604 4, 228 B lfil 119 191 EXAMPLE 3 Twograms alpha-bromobutyric acid were added to 100 grams of a fluidsiloxane having a composition of 75 mol percent dimethylsiloxane units,14 mol percent trimethylsiloxane units, .5 mOlperc'entphenylmethylsiloxane units, and 6 mol percent of dichlorophenylsiloxaneunits. Mixing was readily accomplished by a laboratory stirrer. Thetotal load loss and tooth wear of the. siloxane with and withouttheadditive was determined on the Falex machine after two 5:minuteintervals at 50 pounds, two 5-minute intervals at 100 pounds, and two5-minute intervals at 200 pounds, and found to be as follows:

A fluid siloxane polymer composed of mol percent phenylmethylsiloxaneunits and 10 mol percent'trimethylsiloxane units was tested with andwithout an, additive in the Falex machine over two fiveminute intervalsat 50 pound loads and two five-minute intervals at pound loads with thefollowing result:

A fluid lubricant having excellent lubrication properties at ordinarytemperatures is obtained when 2% by weight (based on the siloxane)diiodoacetic acid is admixed with the siloxane of Example 3.

That which is claimed is:

1. As a composition of matter a mixture consisting essentially of (a) afluid organopolysiloxane having the general unit formula where n has anaverage value of 2.0 to 2.9 and Ris a hydrocarbon radical selected fromthe 'group consisting of methyl, monocyclic aryl, and halogenated arylhydrocarbon radicals and in said siloxane at least 37 percent of thetotal number of R radicals being methyl radicals and (b) 0.25 to 5percent by weight based on the siloxane of a halogenated fatty acid of 1to 12 carbon atoms.

2. The composition of claim 1 wherein R is methyl.

3.. A grease consisting essentially of the composition of claim 1 and aminor amount of a thickening agent.

7 4. As a composition of matter, a mixture consisting essentially of (a)a fluid organopolysiloxane having the average general unit formula 5where n has an average value of 2.0 to 2.9 and R is a hydrocarbonradical selected from the group consisting of methyl, monocyclicaryl,-and halogenated aryl hydrocarbon radicals and in said siloxane atleast 37 percent of the total number of R radicals being methyl radicalsand (b) 0.25 to 5 percent by weight of a halogenated fatty acid of 1 to6 carbon atoms.

5. The composition of claim 4 wherein R is methyl. 6. As a compositionof matter a mixture consisting essentially of (a) a fluidorganopolysiloxane having the general unit formula R,.SiO T where n hasan average value of 2.0 to 2.9 and R is a hydrocarbon radical selectedfrom the group consisting of methyl, monocyclic aryl, and halogenatedaryl hydrocarbon radicals and in said siloxane at least 37 percent ofthe total number of R radicals being methyl radicals and (b) 0.25 to 5percent byweight of a halogenated fatty acid of 1 to 6 carbon atoms andin said acid the halogen being selected from the group consisting ofchlorine and bromine.

7. The composition of claim 6 wherein R is methyl. 8. A greaseconsisting essentially of the composition of claim 6 and a minor amountof thickening agent.

References Cited in the file of this patent UNITED STATES PATENTS2,262,773 Lincoln et a1. Nov. 18, 1941 2,471,850 Wilcock May 31, 1949FOREIGN PATENTS 453,114 Great Britain Aug. 31, 1936 20 September 1949.

1. AS A COMPOSITION OF MATTER A MIXTURE CONSISTING ESSENTIALLY OF (A) AFLUID ORGANOPOLYSILIXANE HAVING THE GENERAL UNIT FORMULA